In a typical exposure apparatus of this type, the light, which is radiated from a light source, forms, via a fly's-eye lens as an optical integrator, a secondary light source as a substantial surface light source composed of a large number of light sources (in general, a predetermined light intensity distribution on an illumination pupil). In the following description, the light intensity distribution, which is provided on the illumination pupil, is referred to as “pupil intensity distribution”. Further, the illumination pupil is defined as the position which makes the illumination objective surface (plane) the Fourier transform plane of the illumination pupil by the aid of the action of the optical system disposed between the illumination pupil and the illumination objective surface (plane) (mask or wafer in the case of the exposure apparatus).
The light, which comes from the secondary light source, is collected by a condenser optical system, and then illuminates a mask, on which a predetermined pattern is formed, in a superimposed (overlaid) manner. The light, which is transmitted through the mask, forms an image on a wafer via a projection optical system, and the mask pattern is projected and exposed (transferred) onto the wafer. The pattern, which is formed on the mask, is fine and minute. In order to correctly transfer the fine pattern onto the wafer, it is indispensable to obtain a uniform illuminance distribution on the wafer.
Conventionally, it has been suggested a technique in which an annular (circular zonal) or multi-pole-shaped secondary light source (pupil intensity distribution) is formed on an illumination pupil defined on a back focal plane of a fly's-eye lens or in the vicinity thereof by the action of an aperture diaphragm which is equipped with a wavelength plate and which is arranged just downstream from the fly's-eye lens, and the setting is made such that the light beam (luminous flux), which passes through the secondary light source, is in a linear polarization state in which the circumferential direction is the polarization direction (hereinafter abbreviated and referred to as “circumferential direction (azimuthal direction) polarization state”) (see, for example, Japanese Patent No. 3246615).
In order to realize the illumination condition suitable to faithfully transfer fine patterns having various forms, it is desired to improve the degree of freedom in the change of the shape (broad concept including the size) of the pupil intensity distribution and the change of the polarization state. However, in the case of the conventional technique described in Patent Document 1, it has been impossible to change the shape of the pupil intensity distribution and the polarization state except if the aperture diaphragm equipped with the wavelength plate is exchanged.
The present teaching has been made taking the foregoing problem into consideration, an object of which is to provide an illumination optical system having a high degree of freedom in the change of the polarization state. Another object of the present teaching is to provide an exposure apparatus and a method for producing a device which make it possible to correctly transfer a fine pattern to a photosensitive substrate under an adequate illumination condition by using the illumination optical system having the high degree of freedom in the change of the polarization state.
According to a first aspect, there is provided an illumination optical system for illuminating an illumination objective surface with light from a light source, the illumination optical system including, a first spatial light modulator which has a plurality of optical elements arranged on a first plane and controlled individually; a polarizing member which is arranged in an optical path on an illumination objective surface side with respect to the first plane and which gives a change of a polarization state to a first light beam passing through a first area in a plane intersecting an optical axis of the illumination optical system, the change of the polarization state being different from a change of the polarization state given to a second light beam passing through a second area in the intersecting plane, the second area being different from the first area; and a second spatial light modulator which has a plurality of optical elements controlled individually and arranged on a second plane in the optical path on the illumination objective surface side with respect to the first plane or in an optical path on a light source side with respect to the first plane, and which variably forms a light intensity distribution on an illumination pupil of the illumination optical system.
According to a second aspect, there is provided an exposure apparatus including the illumination optical system of the first aspect for illuminating a predetermined pattern, wherein a photosensitive substrate is exposed with the predetermined pattern.
According to a third aspect, there is provided a method for producing a device, including, exposing the photosensitive substrate with a predetermined pattern by using the exposure apparatus of the second aspect, developing the photosensitive substrate to which the predetermined pattern is transferred so that a mask layer, which has a shape corresponding to the predetermined pattern, is formed on a surface of the photosensitive substrate; and processing the surface of the photosensitive substrate via the mask layer.